1. Field of the Invention
This invention relates to drilling or boring apparatus and more particularly to means for drilling or boring holes downwardly into the earth.
2. Description of the Prior Art
This invention provides particular advantages when employed in mobile self-propelled drilling apparatus that may be moved from one location to another to drill holes in the earth at different locations as for drilling blast holes; the invention therefore will be described in connection with such apparatus.
Heretofore, drilling apparatus of this type has often comprised a mobile vehicle body having power means for propelling the apparatus, and at one end a drilling mast adapted to be raised to an upright position to permit drilling and to be lowered to a generally horizontal position to facilitate travel of the vehicle from one location to another. The mast has had associated with it means for storing drill rods and placing them into a location where they could be incorporated into a drill string and for removing the drill rods from the drill string and storing them.
In most apparatus of this type, the drill rods are quite heavy, each often weighing several hundred pounds and being 12 to 20 feet long or even longer. The size and weight of these drill rods have prevented handling of the rods manually. Therefore, it is desirable that mechanical means be provided to put stored drill rods into proper position to be connected in the drill string for drilling purposes, and after drilling is finished to disconnect the drill rods from the drill string and store them in drill storage means on the apparatus. Moreover, it is very desirable that this operation be performed rapidly in order to reduce costs of labor, fuel, and to obtain a high rate of usage of the apparatus which usually is quite expensive. It is also important that the handling of the drill rods and the drilling operation be performed with a maximum of safety to operators.
Heretofore, various types of mechanical means have been provided or proposed for handling and storing the drill rods but in general such means has not been as effective as desired, for various reasons.
Prior drilling apparatus, and particularly the means for handling and storing the drill rods have often been excessively complicated and liable to costly break-downs, particularly under the severe conditions of use in the field in which the apparatus is subjected to substantial forces and to dust and abrasion. Prior apparatus often has not been as dependable for these and other reasons, and hence has resulted in added costs of drilling. Often prior apparatus has not operated sufficiently automatically to accurately place the drill rods for inclusion in the drill string, and when the drill rods are removed to place them in storage; often such prior apparatus has required considerable manipulation and control by the operator. These problems have been intensified because of the large inertial forces involved in starting and halting movement of groups of heavy drill rods in the handling and storage means.